The present invention relates to a semiconductor device, and a method for manufacturing the semiconductor device, and for example, a technique that can be applied to a semiconductor device having an AlGaN layer, and a method for manufacturing the semiconductor device.
One of compound semiconductor devices uses a GaN-based semiconductor layer. When an electrode is connected to the GaN-based semiconductor device, it may be preferable that the connection between the electrode and the GaN-based semiconductor device is performed by ohmic contact. The technique for connecting the electrode to the GaN-based semiconductor device is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2000-31540, Japanese Unexamined Patent Application Publication No. 2003-86825, and Japanese Unexamined Patent Application Publication No. 2005-353817.
Japanese Unexamined Patent Application Publication No. 2000-31540 discloses that an Al electrode is connected to an i-layer formed of a GaN layer. Japanese Unexamined Patent Application Publication No. 2000-31540 discloses that a p-type impurity is added to an AlGaN layer (Al may not be eliminated) as an example of a method for forming the i-layer. Also, Japanese Unexamined Patent Application Publication No. 2000-31540 discloses that an Al electrode is connected to the GaN layer added with a high concentration of n-type impurity.
Japanese Unexamined Patent Application Publication No. 2003-86825 discloses that a high carrier layer is formed to bring the GaN layer into ohmic contact with the electrode. An electrode material is exemplified by Al/Ti, Au/Ti, Ti, and Al.
Japanese Unexamined Patent Application Publication No. 2005-353817 discloses that an electrode is brought into ohmic contact with a non-doped Al0.25Ga0.75N layer. This electrode has a structure in which Ti and Al are stacked in the stated order.